An investigation into the impacts of water demand management and decentralized water recycling on excess sewer sediment deposition. (1st February 2021)

• Record Type: Journal Article
• Authors: Murali, Madhu K.; Hipsey, Matthew R.; Ghadouani, Anas; Yuan, Zhiguo
• Is Part Of: Journal of environmental management. Volume 279(2021)
• Publication Date: 2021-02-01
• Subjects: Decentralized water recycling -- Sewer solids -- Sewer sediments -- Urban drainage modelling -- Sediment transport; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2020.111788
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Sewers are a critical part of the urban water system and represent a considerable investment due to the presence of extensive networks in many cities. Consequently, excess sewer sediment deposition, from changed inflow conditions or lack of appropriate sewer infrastructure, can lead to significantly increased maintenance and operational costs. The main aim of this manuscript is to quantify the potential impacts of reduced inflow and increased sediment concentrations from the implementation of sustainable water practices, such as Decentralized Water Recycling and Water Demand Management, on excess sediment deposition in gravity sewers. Experiments in a sewer pilot plant, with municipal wastewater, and modelling using a comprehensive local-scale sewer sediment model were used in conjunction to address this aim. Results from both these methods indicated that a reduction in inflows from the moderate implementation of sustainable water practices had a large impact on the quantity of sediment deposited in gravity sewers. However, further modelling showed that the reduction in bed erosion during peak flows for the same implementations of sustainable water practices occurred more gradually. Overall, our findings showed that in existing gravity sewer mains with reasonable slope and flow velocities, a moderate decrease in peak flow velocity of around 15% due to the implementation of Decentralized Water Recycling and Water Demand Management was unlikely to result in a net increase of sediment deposition. Future work in this area could focus on confirming these findings through case studies in the field or on long-term pilot studies with detailed bed height and density measurements. Graphical abstract: Image 1 Highlights: Pilot sewers showed no increase in deposition from waste activated sludge addition. Low inflow and high sediment scenarios led to significantly increased deposition. Reduction in sediment erosion for equivalent scenarios was much more gradual. ≤ 15% sewer peak flow velocity reduction showed no cumulative sediment increase.